a) Field of the Invention
The present invention relates to alleviating the problem of vortices that form at the outer tips of aerodynamic surfaces, and more particularly the problem of such vortices which are developed by an airplane, especially a rather large airplane, traveling on a flight path, where the vortices can have adverse effects on an airplane which is following (or crossing) that same flight path.
b) Background Art
Current airport capacity is largely controlled by the hours of operation, which are largely confined to daylight hours to prevent noise pollution in the airport environs, and the frequency with which planes can be brought in and out of the airport. A pacing item in landing and takeoff frequency is the time necessary for the dissipation of wake vortices produced by planes in motion. The size and intensity of wake vortices is determined by the size and weight of the aircraft, and pose particularly dangerous conditions in the wake of wide body airplanes. In worst case scenarios, these can be sufficiently dangerous in causing airplane crashes. This problem has been recognized for several decades, and a number of approaches have been suggested to alleviate this problem.
A search of the patent literature has identified a number of patents, these being the following:
U.S. Pat. No. 6,668,638 (Huang) is directed toward controlling the vortex breakdown in an aerodynamic surface of a Delta wing aircraft. For high performance combat aircraft, operating at high incidence and high angular rates, the air flow over the control surfaces is affected by leading edge vortices which are exploited to obtain extra aerodynamic forces. There are moving blowing jets on the upper aerodynamic surface to control this breakdown of vortices and also air may be sucked in from the upper wing surface.
U.S. Pat. No. 6,378,807 (Tomioka) provides jets which blow over the wing for purposes of snow removal.
U.S. Pat. No. 6,283,406 (Remington et al) relates to reducing a high-speed impulsive and blade vortex interaction noise in a helicopter which occurs particularly when the aircraft is hovering so that the vortex of one blade affects the following blade. In one embodiment air intake passages are positioned on the surfaces of each blade proximate to the leading edge and the outer tip to admit air into the interior volume of the blade, and air output passage are disposed on the trailing edge and outer tip portion to expel air.
U.S. Pat. No. 5,813,625 (Hassan et al) relates to noise reduction in a rotorcraft. Pressurized air is directed into the rotor blade and outwardly through a plurality of apertures along a substantial surface area of the rotor blade on both the upper and lower surfaces near the leading edge and also near the tip end of the rotor blade. The pressurized fluid is in a direction generally normal to the blades surface.
U.S. Pat. No. 5,806,807 (Haney) discloses a vortex attenuating airfoil where there is a deflector 40 positioned on the top surface of the wing a short distance inboard of the end tip of the wing, and an air passage extending through the airfoil from an inlet at the lower surface of the airfoil and an outlet on the upper side of the airfoil outboard of the deflector 40.
U.S. Pat. No. 5,755,408 (Schmidt et al) shows a system for creating turbulence at the leading edge surface by ejecting pressurized air selectively, under the control of a microelectromechanical system to affect the turbulence in the boundary layer over that portion of the wing surface.
U.S. Pat. No. 5,158,251 (Taylor) relates to a wing tip vortex alleviating a system where the pressurized air is emitted through a slot 36 which is at the upper outer edge of the wings surface and aligned in a forward to rear direction. The pressurized air emitted from the slot tangentially that curves outwardly and downwardly so that it forms a “Coanda” occurrence (see FIG. 4) that extends in a chordwise direction downward from the Coanda surface 42 perpendicular to the plane of the wing. It is indicated that it is desirable that the Coanda curtain cover as great an area as possible two-dimensionally in both the chordwise (horizontal) and elevational (vertical) direction.
U.S. Pat. No. 4,477,042 (Griswold II) discusses the problem of vortex alleviation that result particularly with heavy aircraft with significant span loading so that the vortex does not adversely effect the aircraft that are following in the wake of the heavier aircraft. To alleviate this problem, the wing tip portion is contoured in one embodiment with an upward slant, and in another embodiment (FIG. 11) in a downward slant. Also, air is discharged through the outer edge of the wing, and this is described in column 6 beginning on line 37 with reference to FIGS. 6 and 7. The air is discharged through a slot 54 and is directed generally tangentially of the tip surfaces 34, 38 so that the flow of air over the surfaces joins the discharged fluid at a comparable velocity and forms a vortex which is lacking the tight laminary core. It is stated that the effect of the discharged fluid alleviates the velocity differentials of the flow and thereby decreases circulation within the vortex region.
U.S. Pat. No. 3,997,132 (Erwin) is directed toward alleviating the problem of wing tip vortices affecting aircraft which are following in the path of the vortex. There are the main jet engines 26 mounted closer to the fuselage, and in each wing tip, there are secondary jet engines 32. These are arranged so that there are guide vanes 70 that are positioned in the annular bypass duct 42. These veins 70 are directed in a manner to counteract the effect of the vortices that is developed at the wing tip.
U.S. Pat. No. 3,984,070 (Patterson Jr) is also directed to the problem of wing tip vortices affecting the aircraft which are following in the vortex. There are retractable plates which have a retracted position within a tubular member, and can be expanded to a radially extending position (FIG. 2) in the vortex dissipating mode.
U.S. Pat. No. 3,974,986 (Johnstone) relates to alleviating the problem of vortices being generated at the wing tip location. There are inlet openings 48 positioned at the lower side of the end edge of the wing, and the high pressure air flows into these openings 48 and into passageways where it is discharged through slots 46 in the upper surface of the wing.
U.S. Pat. No. 3,936,013 (Yuan) relates to the problem of alleviating the problem of vortices at the wing tip locations. At the tip of the wing there is a tubular member 21 which projects laterally outwardly from the end of the wing into the air stream, and there are orifices 22 which blow air into the flow of air in the vortex. In FIG. 3, the flow of the vortex air is illustrated at 24, flowing in an upward direction, and the downward fluid jets 25 that are ejected from the tubular member 21 are indicated at 25.
U.S. Pat. No. 3,881,669 (Lessen) relates to the problem of alleviating the formation of vortices at the outer edge of the outer tip of the wings. This arrangement consists of injecting into the core of the trailing vortex a fluid stream. It is stated in column 3, line 15, that it is essential that the axis of the injected stream be substantially co-linear and co-axial with the longitudinal axis of the trailing vortex.
U.S. Pat. No. 3,841,587 (Freed) relates to the problem of alleviating vortices at the wing tips. There is positioned at the tip of each wing a nozzle assembly 26 that is positioned at the outer trailing edge of the wing and discharges air rearwardly into the core of the vortex. Air is bled from the jet engines to provide the pressurized air. This is a convergent-divergent (i.e. Venturi type) nozzle so that the air in the nozzle reaches sonic velocity at the throat so that the velocity increases to maximum super sonic level in the divergent section of the nozzle from which the air expands outwardly. The nozzle is arranged so that the exhaust passages may be in a configuration to create a new vertical flow of the air in a counter rotating direction relative to the vortex forming at the wing tip. There is a transition from the supersonic back to the subsonic velocity producing a shock wave with an abrupt change in temperature and rapid increase in density of the air in the vortex forming region. It is stated that effects either arrest of the vortex or causes early decay.
U.S. Pat. No. 3,596,854 (Haney Jr.) relates to affecting the vortex developing at the wing tips, primarily for the reason of better aerodynamic control of the airplane. There is at the tip of the wing a housing 10 having a generally cylindrical chamber 11 closed at the front and a discharge orifice 12 at the rear. This causes the air to rotate or swirl in the chamber. This to be done in a manner to increase or decrease lift.
U.S. Pat. No. 3,012,740 (Wagner) relates to an aircraft boundary layer control system where high pressure air is tapped from the engine and is discharged along the wing for improved boundary layer control.
U.S. Pat. No. 2,650,781 (Taylor) shows a system for accomplishing boundary layer control. It is stated that the vortex that is formed at the tip of the wing creates a low pressure area within the core of the vortex. There is an elongated slot 20 at the upper surface of the wing, and this is attached by a duct which leads to the opening at the rear tip portion of the wing. Thus, the air is sucked through the slot to go through this tube and be ejected into the vortex as a means of providing for boundary layer control.
U.S. Pat. No. 3,845,918 (White Jr.) shows a “vortex dissipater” which comprises a fixed flat plate which is mounted at the tip of the wing and is aligned in the direction of the free stream. The plate extends forward from the trailing edge of the tip and outward from the suction side of the lifting surface far enough to reach to the maximum rotational velocity of the vortex.
U.S. Pat. No. 5,150,859 (Ransick) shows an arrangement where a turbine is placed at the wing tip and the trailing vortex that is induced at the wing tip so that the vortex drives the propeller blades which in turn supplies power to such things as the wing de-icing system, etc.
U.S. Pat. No. 5,492,289 (Nosenchuck et al) discloses a “lifting body with reduced-strength trailing vortices.” The trailing edge of the wing is formed with a varying chord length near the tip of the wing, as shown in FIG. 7A where there is a “perturbation” which protrudes rearwardly at 105 at the location of the tip end 102.
U.S. Pat. No. 5,634,613 (McCarthy) shows a wing configuration to alleviate the problems of generating the vortex at the end of the wing by contouring the outer end portion of the wing in a manner to create a “beneficial vortex”. For example, in FIG. 2, which is a view looking straight towards the leading edge of the wing, there is a twist in the forward to rear direction at 66 which gradually changes the airfoil's actual angle of attack from a position angle of attack 68 near the root to a negative angle of attack at the location 70.
U.S. Pat. No. 5,918,835 (Gerhardt) discloses a wingtip vortex device installed at the wingtip of the aircraft, this device having radial fins which are positioned at the location of the vortex so these are caused to rotate by the vortex that shed from the wingtip.
U.S. Pat. No. 6,082,679 (Crouch et al) discloses a system for destruction of trailing vortices, this being accomplished by actuating the control surfaces at the trailing edge of the airfoil in the manner to result in accelerated breakup of the trailing vortices.
U.S. Pat. No. 6,394,397 (Ngo et al), Company, discloses a means of dissipating the vortex by providing an outer edge portion of the wing with a sliding tip member 28 that has a position where it is aligned with the main wing, and a second position where it is moved downwardly from the main wing to extend into the pressure side surface 24 to dissipate the vortex.
U.S. Pat. No. 6,422,518 (Stuff et al), disclose an aircraft with means for breaking down the wing tip vortices, this being accomplished by placing winglets at various locations on the airplane, such as at the fuselage behind the wings, at the tips of the tail in the horizontal plane, or at landing flaps at the inside edges at the wings.
U.S. Pat. No. 6,513,761 (Huenecke), shows a system for reducing vortices in the wake of the aircraft by generating a counteracting vortex or vortices to cause the trailing vortex to “vibrate”. The vibrations of the trailing vortex preferably extend perpendicular to a central longitudinal aircraft axis. Several versions of this are shown in FIGS. 7, 8 and 9. It is indicated in column 6, line 6 that the vortex generators 9 and 10 are preferably auxiliary flaps that are so positioned that the respective counter vortices 13 and 14 interfere with the formation of flap vortices 11B and 12B.